1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.server.net;
18
19import android.os.Handler;
20import android.os.HandlerThread;
21import android.text.TextUtils;
22import android.util.Log;
23
24import java.io.BufferedOutputStream;
25import java.io.DataOutputStream;
26import java.io.FileOutputStream;
27import java.io.IOException;
28
29public class DelayedDiskWrite {
30    private HandlerThread mDiskWriteHandlerThread;
31    private Handler mDiskWriteHandler;
32    /* Tracks multiple writes on the same thread */
33    private int mWriteSequence = 0;
34    private final String TAG = "DelayedDiskWrite";
35
36    public interface Writer {
37        public void onWriteCalled(DataOutputStream out) throws IOException;
38    }
39
40    public void write(final String filePath, final Writer w) {
41        write(filePath, w, true);
42    }
43
44    public void write(final String filePath, final Writer w, final boolean open) {
45        if (TextUtils.isEmpty(filePath)) {
46            throw new IllegalArgumentException("empty file path");
47        }
48
49        /* Do a delayed write to disk on a separate handler thread */
50        synchronized (this) {
51            if (++mWriteSequence == 1) {
52                mDiskWriteHandlerThread = new HandlerThread("DelayedDiskWriteThread");
53                mDiskWriteHandlerThread.start();
54                mDiskWriteHandler = new Handler(mDiskWriteHandlerThread.getLooper());
55            }
56        }
57
58        mDiskWriteHandler.post(new Runnable() {
59            @Override
60            public void run() {
61                doWrite(filePath, w, open);
62            }
63        });
64    }
65
66    private void doWrite(String filePath, Writer w, boolean open) {
67        DataOutputStream out = null;
68        try {
69            if (open) {
70                out = new DataOutputStream(new BufferedOutputStream(
71                        new FileOutputStream(filePath)));
72            }
73            w.onWriteCalled(out);
74        } catch (IOException e) {
75            loge("Error writing data file " + filePath);
76        } finally {
77            if (out != null) {
78                try {
79                    out.close();
80                } catch (Exception e) {}
81            }
82
83            // Quit if no more writes sent
84            synchronized (this) {
85                if (--mWriteSequence == 0) {
86                    mDiskWriteHandler.getLooper().quit();
87                    mDiskWriteHandler = null;
88                    mDiskWriteHandlerThread = null;
89                }
90            }
91        }
92    }
93
94    private void loge(String s) {
95        Log.e(TAG, s);
96    }
97}
98
99